1. Field of the Invention
The present invention is directed to a physiological recording device and, more particularly, to configurations thereof maximizing performance while minimizing material cost, and that can be used without skin preparation or the use of electrolytic gels. The invention is further directed to an encouragement ring which stabilizes and helps situate the physiological recording device on a subject's skin to help provide a better electrical signal, increase surface area, and reduce and minimize noise and artifacts during the process of recording or monitoring a physiological signal. The invention is still further directed to surface features on a surface of the physiological recording device with a size and shape that will not substantially bend or break, which limits the depth of application of the recording device, and/or anchors the recording device during normal application. The invention is even further directed to a method for manufacturing a physiological recording device, and minimizing cost of manufacture.
2. Technical Background
Electrodes for measuring biopotential are used extensively in modern clinical and biomedical applications. These applications encompass numerous physiological signal acquisition and monitoring modalities including electrocardiography (ECG), electroencephalography (EEG), electrical impedance tomography (EIT), electromyography (EMG) and electro-oculography (EOG). The electrodes for these types of physiological tests function as a transducer by transforming the electric potentials or biopotentials within the body into an electric voltage that can be measured by conventional measurement and recording devices. Such electrodes traditionally required preparation of the skin in order to increase the quality of the transmitted/recorded signal. Such preparation may include removing hair, abrading the skin, and/or application of electrolytic fluids or gels. However, more recently, “dry” electrodes, requiring no electrolytic fluids or gels, have been developed which eliminate the need for skin preparation in order to transmit higher quality signals.
Both traditional “wet” electrodes and existing varieties of “dry” electrodes give rise to issues in recording of physiological biopotential signals. Whereas existing varieties of dry electrodes improved over wet electrodes by eliminating the need for messy electrolytic gels, these dry electrodes still suffer from their own shortcomings. Most notably, manufacturing costs of those devices are traditionally very high, making production on a large scale difficult and not very cost effective. These electrodes typically need to be made from expensive polymers which are typically non-conducting. The overall expense of the electrode is increased significantly over the cost of just the base polymer material by the requirement of adding a conductive coating and/or ionic compound to the entire surface of the electrodes in order to ensure an electrical pathway exists whereby the biopotentials may be transferred from the patient or subject to the appropriate monitoring equipment. The most common conductive coating and/or ionic compound used in electrodes, and particularly to coat dry electrodes, is silver/silver chloride (Ag/AgCl), which is preferable due to its high biocompatibility and conductivity properties. This Ag/AgCl coating will not harm the patient, nor generally cause any adverse reactions, while still providing the high conductivity required for transmitting the biopotential across an otherwise non-conductive electrode body. The compound of silver chloride itself is approximately 75.2% silver. Thus, when a combination of silver and silver chloride is used, a large percentage of silver is actually required to coat the entire electrode surface to meet the conductivity requirements for using such electrodes to transmit biopotentials. Typically, dry electrodes are monolithic in nature, that is, constructed in a single piece, and coated about their entirety in a conductive or ionic compound such as Ag/AgCl. Thus, these dry electrodes, while addressing many disadvantages of traditional “wet” electrodes, are expensive to manufacture, and thus present some obstacles in actually being adopted over traditional electrodes in spite of the shortcomings thereof, which are much less expensive.
Therefore, an object of the present invention is to provide a dry electrode that is significantly less expensive to manufacture and produce than prior dry electrodes. It is further an object of the present invention to provide a dry electrode that minimizes the amount of expensive conductive coatings or ionic compounds required to accurately and effectively transmit biopotentials. It is still further an object of the present invention to provide a separate encouragement ring, constructed of a separate and less expensive material, which helps to reduce cost and also provide stability to the device when placed on a subject's skin.
In view of the foregoing inherent disadvantages with presently available wet and dry electrodes, it has become desirable to develop an electrode that does not require skin preparation or the use of electrolytic gels and overcomes the inherent disadvantages of presently available dry electrodes.